A printer which performs printing information such as a desired character or image on a sheet-like printing medium such as a paper sheet or film is widely used as an information output apparatus in a wordprocessor, personal computer, facsimile apparatus, and the like.
Various methods are known as printing methods in the printer. Especially an ink-jet method has recently received a great deal of attention because this method can realize noncontact printing on a printing medium such as a paper sheet, easily prints in color, and is quiet. Because of low cost and easy downsizing, a popular ink-jet arrangement is a serial printing system in which a printhead for discharging ink in accordance with desired printing information is mounted and prints while the printhead is reciprocally scanned in a direction perpendicular to the convey direction of a printing medium such as a paper sheet.
In order to widen a region printed by one scanning and increase the printing speed, the printhead of the ink-jet printer has many printing elements (nozzles) arrayed in almost the same direction as the printing medium convey direction. The ink-jet printer generally comprises a plurality of printing element arrays or printheads in correspondence with a plurality of inks for use for color printing and/or multitone printing.
In general, image data from a host device such as a personal computer is transmitted as raster data of one line that is rasterized in the scanning direction (horizontal direction). The printer which has received the raster data performs H-V conversion of rearranging image data in accordance with the printing element array direction (vertical direction).
In order to stably discharge ink at high speed from an ink-jet printer, the ink-jet printer adopts distributed discharge control of controlling to simultaneously discharge ink from a plurality of nozzles arrayed at specific intervals, instead of simultaneously discharging ink from all nozzles.
When the ink-jet printer using distributed discharge control prints by color printing or the like using a plurality of inks, data management and distributed discharge driving control are executed for each ink used.
For example, in a color printer using three color inks of yellow, magenta, and cyan which are three primary colors in subtractive color mixing, the control circuit is constituted in accordance with the arrangement (the number of nozzles, the positional relationship of the printheads, and the like) of the printhead for each color. When printheads have different arrangements, the control circuit is changed in accordance with each arrangement.
In recent years, ink-jet printers are increasingly used for various purposes, and demands have arisen for higher printing speed and higher image quality. In this situation, the printhead arrangement varies in accordance with the application and purpose.
To facilitate the development and realize low cost, it is desirable to design a control circuit capable of coping with various printhead arrangements.
More specifically, the control circuit is so designed as to arrange a buffer memory for each printhead and generate data to be transferred to the head. Due to various printhead arrangements, the control circuit takes a different circuit arrangement for the arrangement of each printhead for use, and cannot be utilized in a printhead having another arrangement.
For example, in the simplest arrangement in which a buffer memory for storing data to be printed by one scanning is arranged for each printhead (ink), the capacity of the buffer memory changes in accordance with the printing medium size and resolution used for printing. When the buffer memory is formed in a very large scale integrated circuit (VLSI) for higher processing speed, the buffer memory occupies most of the region on the VLSI. If the buffer memory is downsized, but a plurality of types of buffer memories are formed in correspondence with printheads with a plurality of arrangements, the physical region occupied by the memories inefficiently increases.
Some control circuits are so configured as to simultaneously access data at a plurality of addresses in order to efficiently access the memory in accordance with the printhead specifications. Such circuit comprises, e.g., a register and counter for setting the start address, as shown in FIG. 11. By using the counter, data in number set at the counter can be accessed from a desired address.
However, this circuit arrangement limits the specifications of a compatible printhead. Depending on the contents of a specification change, the control circuit must be changed.
As described above, it is difficult for printheads with various arrangements to commonly employ a control circuit for the printhead and a large-scale logical circuit including the control circuit. The control circuit of the printhead inhibits efficient development and low-cost apparatuses.